The present is directed to night vision scopes and more particularly to an improved optical system for night vision video cameras in which a pair of mirrors provide a high speed and high resolution image to an image intensifier located between the mirrors, without the need for corrective lenses. The system is scalable to a diverse range of sizes and is suitable for rugged duty, such as police and military surveillance work.
Various types of night vision scopes are known. Typically, the image viewed by the night vision scope is reflected and/or refracted to an image intensifier that enhances the received image. The image intensifier permits the image to be viewed in low light level conditions, such as those encountered at night. The optical system of the night vision scope must have sufficient light gathering power (i.e., a low f-number with few optical aberrations) so that the image intensifier can provide a viewable image. Further, the optical system should provide an image resolution that is at least as good as, and preferably better than, the image resolution of the image intensifier. Image intensifiers suitable for night vision video cameras typically have a resolution of about 28-40 line pairs per millimeter.
The need to provide a high speed and suitably resolved image to the image intensifier has driven the development of night vision scopes to more complex optical systems. However, such complex systems require the use of aberration-introducing lenses. In an effort to do away with such lenses, other systems limit the number of reflections to one. These efforts tend to reduce the range capability of night vision video cameras. See, for example, the limited range system in U.S. Pat. No. 4,629,295 to Vogel.
Other optical systems that provide a pair of mirrors to reflect an image to a image viewing device do not have the speed and/or resolution required for night vision video cameras. See, for example, U.S. Pat. No. 2,817,270 to Mandler in which a telescope objective system provides a speed of only f/9, too slow for use with the night vision video camera. This is also true for the device in U.S. Pat. No. 4,282,527 to Winderman, et. al.
Accordingly, it is an object of the present invention to provide a novel optical system for a night vision video camera that obviates the problems of the prior art.
It is a further object of the present invention to provide a novel optical system for a night vision video camera that has an optical prescription that provides a high speed image with appropriate resolution to an image intensifier.
It is yet a further object of the present invention to provide a novel optical system for a night vision video camera that provides a high speed optical system in a novel, easy to manufacture structure suitable for rugged duty.
It is another object of the present invention to provide a novel night vision video camera having a lens-less optical system that provides a high speed, suitably resolved image to a video camera.
These and many other objects and advantages of the present invention will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of preferred embodiments.